Sorry I don't have answers either right now. But you must be patients it would probably mean that we all are trying to figure that out ourselves. The only thing I found out is that after you defeat the giant bat you must have you latchhook Shut Gun and act like that you are going back outside but don't they will be a msesage that for you to read and it would be best to use Billy on the Latch Hook gun. Cause right when you get up there Billy will have to push another bookshelf.. Well this is how far I've got in the game myself at last.